1. Technical Field
The present invention relates to a three-dimensional measuring apparatus, method, and program for projecting a predetermined pattern of light onto an object for non-contact measurement of three-dimensional information.
2. Background Art
In a variety of fields such as medical care, beauty care, apparel design of clothes as well as shoes, eye glasses, or hats, diet control, and health care, in recent years there have been demands for acquiring three-dimensional shape data not only regarding the torso but also regarding the entire human body including the face, the head and the limbs. Thus, expectations are placed on the development of an apparatus for non-contact high-speed measurements of three-dimensional shapes.
Three-dimensional measurement techniques are divided into two types: a passive type for making measurements without illuminating a measurement object with specific light or radio waves serving as an aid for measurement, and an active type for illuminating a measurement object with light, sound waves, or radio waves to utilize the resulting information for measurement.
Heretofore, many methods for making three-dimensional measurements by illuminating a measurement object with a pattern of laser light have been suggested and put into practical use. However, because laser light is likely to have adverse effects on the human body, these methods are difficult to apply to the human body. For example, Patent Document 1 describes a three-dimensional measuring method which has been improved by reducing, for example, the intensity of laser light as much as possible. However, a reduction in the intensity of laser light, in turn, requires an increase in the time of exposure to it, thereby resulting in the total amount of laser light being increased. Accordingly, it is desired to establish a three-dimensional measuring method for the human body without using a laser.
An example of a human body shape measuring apparatus that employs an active three-dimensional measuring method without use of laser light is described in Non-Patent Document 1. This human body shape measuring apparatus utilizes a time series spatial coding method in which seven types of coded patterns of light (gray code patterns) formed by a stripe-shaped light shutter array are projected onto a measurement object to optically divide the object, thereby computing the coordinates of the measurement object on the principle of triangulation.
However, the human body shape measuring apparatus described in Non-Patent Document 1 requires multiple projections for a single measurement. Accordingly, a substantial number of projections are required for highly accurate measurements. For example, the time series spatial coding method used in the human body shape measuring apparatus described in Non-Patent Document 1 requires at least seven projections in order to provide an improvement in measurement accuracy by 1% in the direction of depth. In the measurement of a human body, the subject is difficult to keep still for a long time during the measurement, and thus it is preferable that the number of projections be reduced as much as possible to shorten the time required for three-dimensional measurements.
In this regard, to solve the aforementioned problems, the inventor and others have devised a three-dimensional measuring method based on a monochrome projection & color analysis technique (see Non-Patent Document 2). According to the monochrome projection & color analysis technique, a monochrome-based pattern of light is first projected onto a measurement object. Then, in order to obtain as much information as possible on the intensity of the reflected light, a digital camera is used to capture the projected (observed) pattern of light. The color channel of each pixel in the captured color projected pattern light image is analyzed to employ a color channel that provides the most intense reflection as the measurement channel of the corresponding pixel, thereby making up a digital image having a high intensity distribution. The direction angle of the projected pattern of light is determined from the intensity distribution of each individual pattern (stripe) which forms the projected pattern of light detected on the computation image, thereby computing the three-dimensional information on the measurement object.
[Patent Document 1] Unexamined Japanese Patent Publication No. 2003-11430.
[Non-Patent Document 1] Susumu Shibata, Koichiro Yamauchi, Yuji Nishio, Takashi Futagawa, and Yukio Sato, Proceedings of the 10th Symposium on Sensing via Image Information, Technical Committee on Sensing of Image Information, pp. 253-258, Jun. 9, 2004.
[Non-Patent Document 2] Genki Cho and Cunwei Lu, “3-D Image Measurement Techniques by Combination of MPCA and OIMP for Improvement of the Measurement Efficiency”, Proceedings of the 10th Symposium on Sensing via Image Information, Technical Committee on Sensing of Image Information, pp. 53-58, Jun. 9, 2004.